The present invention relates to a benzylpiperidine compound useful as a production intermediate for a cyclic amide compound and the like used as a therapeutic agent for acquired immunodeficiency syndrome and a production method thereof.
As synthetic methods of benzylpiperidine compounds, (i) a method via reduction of carbonyl group (Wolff-Kishner reduction, etc.) after Friedel-Crafts reaction and (ii) a method via olefin synthesis reaction such as Wittig reaction and Horner-Emmons reaction etc. as shown in the following are known.
(i) The method of A. Wick et al. (U.S. Pat. No. 4,690,931, 1987) 
(ii) The paper of Z-L Zhou et al. (J. Org. Chem., 1999, vol. 64, p. 3763) 
Of the benzylpiperidine compounds, particularly when a compound where a carbamoyl group substitutes on the benzene ring is to be synthesized, a method that goes through an olefin synthesis reactions such as Wittig reaction and the like is advantageous in that the position of substitution can be controlled easily. However, it is not known that benzylpiperidine compounds substituted by a carbamoyl group having an acidic hydrogen disadvantageous to the reaction can be produced through those reactions.
In addition, Takayanagi et al. (WO98/31661) obtained a benzylpiperidine compound substituted by methoxycarbonyl group, and thereafter converted the methoxycarbonyl group to a substituted carbamoyl group.
When this example described in WO98/31661 and an azidation reaction are combined, a carbamoyl-substituted benzylpiperidine compound can be synthesized as shown by the following formulas. 
wherein HOBt is hydroxy-1H-benzotriazole and WSC is 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide hydrochloride.
However, the production method is complicated, and the development of an industrially advantageous short-step production method is necessary.
In view of the above, it is an object of the present invention to provide an industrially advantageous short-step production method of a benzylpiperidine compound wherein a carbamoyl group substitutes on the benzene ring, and to provide a novel synthetic intermediate for this production method.